The present invention is directed to an apparatus for growing farm animals such as poultry in an indoor environment, and in particular, is directed to an apparatus for efficiently heating and ventilating a farm enclosure.
In the poultry industry; as well as other industries where domesticated fowl are cared for in an indoor environment, the temperature and ventilation of the environment must be carefully managed. However, proper heating of the indoor environment may complicate the problems associated with ventilation. Similarly, proper ventilation may cause problems in heating the indoor environment. Therefore, it is necessary to strike a proper balance between the two.
The poultry industry has typically utilized a specific arrangement of brooder heaters, exhaust fans and curtains to facilitate the proper heating and ventilation of a poultry house. The brooder heaters are special heating units which provide the necessary heat for the poultry house and are sized according to the number of chickens the house can hold. At a minimum, one 30-40,000 BTU brooder heater should be utilized for every 750 chickens. These brooder heaters can be staggered down the center of the poultry house or, alternatively, staggered from side-to-side throughout the house. The brooder heaters use fully-on or fully-off type burners.
The exhaust fans of a typical poultry house are placed along the length of one of the poultry house walls. In most houses, the exhaust fans are mounted along the North wall. Due to the rigorous ventilation requirements, the exhaust fans employ 36" diameter blades.
The curtains of this type of poultry house are disposed along one side of the house opposite the exhaust fans as well as between the exhaust fans. Together, the curtains and exhaust fans provide the necessary cross-flow ventilation. At a minimum, four fans must be used with separate timers and overrides in houses greater than 350' in length. To provide the necessary ventilation while attempting to maintain heating efficiency, the exhaust fans are operated in a cyclic fashion. In most houses, the exhaust fans are on for a period of two minutes followed by an 8 minute off period.
Many poultry houses of this type are provided with a brooding section which is partitioned off from the rest of the house. Due to the added ventilation requirement of the chicks, two fans are locating in such a brooding section.
Baby chicks, in particular, are extremely sensitive to temperature changes that occur within the poultry house. Any temperature changes prove to be extremely critical during the first three weeks of the six-week grow-out period, which is the time it takes for a baby chicken to grow to a sufficient size for processing. During the grow-out period, as little as a 10.degree. F. temperature deviation may stunt the growth of a chick and cause a chick to experience poor feed conversion, which is the ratio between the amount of food used to feed a chicken per pound of weight of the full grown chicken. The baby chicks are often exposed to such temperature deviations when they wander away from the brooders. Therefore, it is imperative to maintain the temperature throughout the poultry house at a relatively constant level for the duration of the grow-out period.
There are certain known temperatures at which chicks will experience optimal growth and feed conversion. Specifically, during the first three weeks of a typical grow-out period, the poultry house, or brooding section thereof, should be maintained at a temperature that is no less than 85.degree. F. During the second three weeks of a grow-out period, this temperature level should be maintained no less than 72.degree. F.
Ventilation of a poultry house serves three main purposes. First, proper ventilation removes moisture from the indoor environment of the house. Second, proper ventilation removes poisonous gases, such as ammonia and carbon dioxide, from the indoor environment of the poultry house. The ammonia is generated by the baby chicks when their feces are mixed with the moisture laden make-up air and wood chips or rice hulls on the house floor. In an average poultry house, three hundred pounds of chick manure is produced over a 24 hour period which causes a high humidity environment further perpetuating the harmful effects of the ammonia gases which also further promotes the growth of bacteria and fungi. Carbon dioxide is also present in a poultry house as a result of normal respiration. Third, proper ventilation provides fresh breathable air for the chickens. Overall, the air in a poultry house must be exchanged at least four times per hour to supply the baby chicks with enough breathable fresh air to survive.
Feed expenses account for 60% of the cost of producing chickens. Therefore, a proper starting point for optimizing the chicken production process should focus on the feed and its associated variables such as weight of the chickens and feed conversion.
Proper heating and ventilation of a poultry house can have a significant effect on the weight and feed conversion of chickens and, as a result, on the feed costs. When the temperature is too cold, the feed is consumed and converted to body heat rather than tissue for growth. The maximum feed conversion during the six week grow-out period is achieved at 85.degree. F. and 72.degree. F., which are the temperatures noted above. Thus, it must be recognized that there is a delicate balance necessary between eliminating the moisture and gases from the poultry house, while at the same time providing the proper ventilation and warmth for the baby chickens. As noted, the heating and ventilation of the poultry house influences the weight and feed conversion of the chickens. For example, where the chickens are of a good weight but experience poor feed conversion, the house is likely too cool causing a waste of feed from the feeders. Where the chickens are light in weight but experience acceptable feed conversion, the poultry house is likely too warm and the chickens are therefore not receiving sufficient feed or water. If the chickens are light in weight and are further experiencing poor feed conversion, the poultry house ventilation is likely inadequate which causes a build-up of ammonia affecting the growth of the chickens.
The focus of the policies with respect to management of heating and ventilation of poultry houses has in the past been primarily concerned with lowering fuel bills. This perspective loses sight of the most important factor of the grow-out period which is chick comfort. By being overly concerned with energy savings, the chicks are exposed to an unstable environment of sudden temperature changes and improper ventilation thereby causing illness, and even death, among the chicks.
During cold weather operation, growers of chickens are often instructed to keep the curtains closed so that fresh air may be pulled through the cracks and crevices of the house when the exhaust fans are turned on. This policy of keeping the curtains closed, in conjunction with the cycle operation of the exhaust fans, causes two primary problems. First, cold air from the outside is immediately directed through the curtains to the floor when the exhaust fans turn on. Since the temperature of the poultry house is typically warmer than the cold outside air, the baby chicks experience a shock due to the sudden change in temperature. As a result of the influx of cold air, the brooder heaters turn on to raise the poultry house temperature to the proper level. However, at the same time that the brooder heaters are increasing the poultry house temperature, the ammonia and carbon dioxide gas levels as well as the humidity level inside the poultry house are also increasing.
Second, the cyclic exhaust fan operation and the closed curtains cause the poultry house to assume a negative air pressure in comparison or with respect to the ambient outside pressure. Consequently, this generates an improper air flow throughout the poultry house. Additionally, the cyclic operation of the exhaust fans submits the baby chicks to periods of stagnant, ammonia laden, high humidity conditions for about 80% of the time.
U.S. Pat. No. 5,123,592, issued to one of the inventors of the present invention, discloses a method and apparatus for growing poultry or other domesticated fowl in an indoor environment. In this patent, the apparatus more efficiently heats and ventilates a poultry house when combined to conventional techniques. The method disclosed describes utilizing such an apparatus for heating and ventilating a poultry house. The apparatus included an energy exchange unit using the thermal energy of the exhaust air drawn from the poultry house to pre-heat the incoming fresh air supplied to the poultry house. The energy exchange unit had an exhaust air inlet which receives the exhaust air from the poultry house, an exhaust air outlet which releases the exhaust air to the outdoors, a fresh air inlet which receives the cool fresh air from the outdoors, and a fresh air outlet which supplies pre-heated fresh air to the poultry house. The unit included baffles to transfer heat from the exhaust air to the fresh incoming air.
Several possible issues exist in this patented apparatus and method. One such issue is in the difficulty of cleaning and washing the interior of the energy exchange unit. Another possible issue in the patented apparatus and method is in the overall operational efficiency of the thermal exchange unit. Efficiency is relatively low, on the order of about 35%, in terms of thermal heat exchange. An additional possible issue is in the assembly of the unit described in the patent. Additionally, though the patented unit improves the air quality and reduces thermal shock within a poultry house, improvement may be needed in the above two areas.
Thus, it will be recognized that the poultry house environment is in a continuous cycle of change. When the poultry house temperature drops, the brooder heaters turn on. When the brooder heaters turn on, the humidity, ammonia and carbon dioxide concentration levels increase. When those levels increase in this stagnant air condition, the exhaust fans turn on for 2 minutes and then off for 8 minutes. Nothing in the poultry house environment remains constant. The chickens are either too cold or too warm and they are either breathing fresh air for 2 minutes or hot stagnant air for 8 minutes. This ever-changing environment causes illness and death to chickens throughout the entire poultry house. Although the patented heat exchanger apparatus and method significantly improved these conditions, further improvement is necessary in the above mentioned deficient areas.
There is therefore a need in the art for an apparatus for heating and ventilating a poultry house which improve the deficiencies of the conventional techniques and the earlier patented technique described above.